We have taken both kids around that age (one was 19 months and the other 21 months) and never used a booster or high chair at Sci-Fi. Since it was just 2 adults the first time and a toddler, he sat between us and did fine. The next time DD went, she stood or knelled on the seat and in general is much too active for a booster. But they do have them but if there are 3 of you, you will have one kids in one row of seats and the other in a different row. (Most rows only fit 2 - maybe three if it is children or small adults with kids.)